參數(shù)資料
型號(hào)： MAX1515
廠商： Maxim Integrated Products, Inc.
英文描述： Low-Voltage, Internal Switch, Step-Down/DDR Regulator
中文描述： 低電壓、內(nèi)置開(kāi)關(guān)、降壓型/DDR穩(wěn)壓器
文件頁(yè)數(shù)： 19/24頁(yè)
文件大?。?/td> 504K
代理商： MAX1515
M
Low-Voltage, Internal Switch,
Step-Down/DDR Regulator
______________________________________________________________________________________
19
While sourcing current, V
CHG
and V
DISCHG
increase
with source load current and the voltage across the
inductor decreases. This causes the frequency to drop.
Conversely, while sinking current, V
CHG
and V
DISCHG
decrease with sink load current and the voltage across
the inductor increases. Approximate the change in fre-
quency with the following formula:
where R
DROP
is the resistance of the internal MOSFETs
(40m
Ω
typ) and the inductor.
Inductor Selection
The key inductor parameters must be specified: induc-
tor value (L) and peak current (I
PEAK
). The following
equation includes a constant, denoted as LIR, which is
the ratio of peak-to-peak inductor AC ripple current to
maximum DC load current. A higher value of LIR allows
smaller inductance but results in higher losses and rip-
ple. A good compromise between size and losses is
found at approximately a 25% ripple-current to load-
current ratio (LIR = 0.25), which corresponds to a peak
inductor current 1.125 times the DC load current:
Additionally, the minimum inductance chosen must be
high enough to limit the inductor current during the
high-side switch on-time to less than 1A/μs.
The peak-inductor current at full load is 1.125 x
I
OUT(MAX)
if the above equation is used; otherwise, the
peak current is calculated by:
Choose an inductor with a saturation current at least as
high as the peak-inductor current. The inductor select-
ed should exhibit low losses at the chosen operating
frequency.
Input Capacitor Selection
The input-filter capacitors reduce peak currents and
noise at the voltage source. Place a low-ESR and low-
ESL 0.1μF capacitor for noise filtering no further than
5mm from IN. Select the bulk input capacitor according
to the RMS input ripple-current requirements and volt-
age rating:
Output Capacitor Selection
The output filter capacitor affects the output-voltage
ripple, output load-transient response, and feedback-
loop stability. For stable operation, the MAX1515
requires a minimum output ripple voltage of V
RIPPLE
≥
1% x V
OUT
. The minimum ESR of the output capacitor
is calculated by:
Stable operation for source-only applications requires
the correct output filter capacitor. When choosing the
output capacitor, ensure that:
For DDR applications, the output capacitance require-
ment needs to be two times the above requirement.
The output filter capacitor must have low enough equiv-
alent series resistance (ESR) to meet output ripple and
load-transient requirements, yet have high enough ESR
to satisfy stability requirements.
For applications where the output is subject to violent
load transients, the output capacitor’s size depends on
how much ESR is needed to prevent the output from
dipping too low under a load transient. Ignoring the sag
due to finite capacitance:
In applications without large and fast load transients,
the output capacitor’s size often depends on how much
ESR is needed to maintain an acceptable level of out-
put voltage ripple. The output ripple voltage of a step-
down controller equals the total inductor ripple current
multiplied by the output capacitor’s ESR. Therefore, the
maximum ESR required to meet ripple specifications is:
R
V
I
LIR
ESR
RIPPLE
(
OUT MAX
≤
)
R
V
I
ESR
STEP
OUT MAX
(
≤
)
Δ
C
V
t
V
F
s
OUT
REFIN
OFF
OUT
≥
×
×
/
105
μ
μ
ESR
L
t
OFF
%
1
≥
I
I
V
V
V
V
RMS
OUT MAX
(
OUT
IN
OUT
IN
=
(
)
)
I
I
V
t
L
PEAK
OUT MAX
(
OUT
OFF
=
+
×
×
)
2
L
V
V
s
A
MIN
IN MAX
(
OUT
)
×
)
≥
(
1
1
μ
L
V
t
×
I
LIR
OUT
OFF
OUT MAX
(
=
×
)
Δ
f
I
R
t
V
PWM
OUT
DROP
IN
OFF
×
=
×
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
MAX1515ETG 功能描述:直流/直流開(kāi)關(guān)調(diào)節(jié)器 RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開(kāi)關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5
MAX1515ETG+ 功能描述:直流/直流開(kāi)關(guān)調(diào)節(jié)器 3A 1MHz Step-Down DDR Regulator RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開(kāi)關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5
MAX1515ETG+T 功能描述:直流/直流開(kāi)關(guān)調(diào)節(jié)器 3A 1MHz Step-Down DDR Regulator RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開(kāi)關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5
MAX1515ETG-T 功能描述:直流/直流開(kāi)關(guān)調(diào)節(jié)器 RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開(kāi)關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5
MAX1515EVKIT 制造商:Maxim Integrated Products 功能描述:3A 1MHZ LOW-VOLTAGE INTERNAL SWI - Rail/Tube
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